This application relates generally to the field of automobile sensors and more particularly to compensating output of ultrasonic sensors.
An obstruction detection system for a vehicle generally employs sensors such as ultrasonic sensors mounted on the vehicle body for detecting surrounding obstacles using ultrasonic waves. Conventionally, the ultrasonic sensors transmit sound waves around the vehicle and sense an obstacle through waves reflected by the obstacle. To this end, the sensor determines the time lag in receiving the reflected sound wave, and using the known speed of sound, identifies the distance between the obstacle and vehicle.
It should be understood that in dry air, at 20° C. (68° F.), the speed of sound is 343 meters per second. Weather conditions, however, affect the behavior of the sound waves, and the speed of sound varies with pressure, temperature, and humidity. Ultrasonic sensors are generally employed in a number of vehicles to provide parking assistance, collision detection, auto-parking, or any other kind of obstruction avoidance capabilities. Consequently, appropriate obstruction detection is required to avoid damaging the vehicle.
Currently, the speed of sound is compensated for atmospheric temperature variations by employing an ambient temperature sensor mounted on the vehicle. This may be expensive, however. In addition, no existing solution compensates the ultrasonic sensor for atmospheric pressure variations.
It would be highly desirable to have a cost-effective and efficient system that compensates an ultrasonic sensor for speed of sound variations arising due to atmospheric variations.